Flammable liquids and gases are commonly stored in or transmitted through metallic structures such as tanks and pipelines, and, especially in electrolytic environments (such as soils, moisture, etc.) such metallic structures have a tendency to corrode.
One of the most deleterious forms of corrosion of metal structures occurs when these structures are exposed to the electrolytic action of a conductive environment. While not wishing to be bound by any particular theory, it is believed that electrochemical corrosion results from the flow of current from one area of the metal structure (anodic area), through the conductive environment, to another area on the same structure (cathodic area), thereby completing the circuit of a miniature electrolytic cell. At the anodic areas, the metal is oxidized to a positive valence state and leaves the surface in ionic form, ultimately leading to pitting and other forms of gross degradation of the metal. Electrochemical corrosion is generally encountered when metal structures such as tanks and pipelines are buried in the ground or when such structures as ship hulls and off-shore platforms are submerged in sea water. In order to limit corrosive effects under these circumstances, methods for cathodic protection of metal structures have been developed which rely on an external current source or a sacrificial anode to impose a negative electrical potential on the metal structure relative to its surroundings. This is believed to effectively turn the whole structure into a cathode, thereby reducing, or eliminating, current flow from the structure to the conductive environment, and thus the corrosion associated therewith.
Cathodic protection might entail the connection of an elongated electrically conductive wire between a storage tank or transmission pipeline metallic structure and the external source of electrons. The electrons source might be an electrical generator apparatus or even simply an anodic chemical element (e.g. magnesium, zinc, etc.) having an empirical rating on the "Electromotive Force Series of Metals" (i.e. EMS) that is relatively higher than is the EMS rating for the metallic structure. However, as is appreciated in the prior art, connecting the elongate wire to a tank or pipeline metallic structure invariably necessitates the very expensive fire-prevention step of initially purging the flammable fluid prior to making a mechanical or high-temperature connection to the tank or pipeline. For example, mechanical connections deliberately puncture the tank or pipeline, and welds or chemically exothermic processes are apt to produce hairline cracks in the metallic tank or piping; in either case, the escaping flammable fluid can ignite to endanger the workers and environs.
Some examples of metallic structures which are prone to the phenomenon of spontaneous corrosion are: radiating panels embedded in floor concrete; metallic pipes embedded in or passing through masonry; and standing, fixedly mounted metallic piles. All of these metallic structures may come into contact with water or some other electrolyte. Moreover, metallic structures which are exposed to the atmosphere are also susceptible to spontaneous corrosion. For instance, eaves, gutters, motor vehicle parts etc. are all subject to this phenomenon.
Other prior art methods of connecting a cathodic protection device to a metallic structure include the method described in U.S. Pat. No. 4,685,752 (MATERIALS PROTECTION COMPANY) wherein the cathodic protection device is attached to a metallic surface by an adhesive and conductive contact is then achieved by turning a screw cap, having an electrically conductive terminal member attached thereto, in a downward direction until contact is made between the terminal member and the metallic surface.
Unlike the prior art, this invention provides cathodic protection devices that are easily and quickly connected to metallic surfaces. These devices comprise a suction cup and adhesive(s). The suction cup allows the cathodic protection device to be quickly attached to a metallic surface and, without the requirement for any other action, provides the device with sufficient residence time on the surface to allow the adhesive(s) to bond the cathodic protection device to the metallic surface.